A display device such as a liquid crystal display has a structure in which a liquid crystal layer is interposed between two substrates formed with a pair of electrodes facing each other. A color filter composed of red (R), green (G), and blue (B) pixel regions is formed inside one substrate. In this color filter, a black matrix is usually formed so as to define each of red, green, and blue pixel regions.
In general, the color filter is produced by a lithographic method. First, a black photosensitive composition is applied on a substrate, dried, exposed, and then developed to form a black matrix. Then, coating, drying, exposure, and development are repeated every photosensitive composition of each color of red, green, and blue, and each pixel region is formed at a specific position to produce a color filter.
In recent years, there have been trials made for further improving contrast of an image to be displayed on a liquid crystal display by improving light shielding property due to a black matrix in the production of a liquid crystal display. For this purpose, there is a need for a photosensitive composition for formation of a black matrix to contain a large amount of a light shielding agent. However, if the photosensitive composition contains a large amount of the light shielding agent, it becomes difficult for light for curing the photosensitive composition to reach the bottom of a film of the photosensitive composition applied on a substrate when the film is exposed to light, leading to undercure associated with significant deterioration in sensitivity of a curable composition.
In the photosensitive composition, a photopolymerization initiator contained as a portion of the components generates radicals upon exposure. The radicals cause polymerization of a polymerizable compound contained in the photosensitive composition, leading to curing of the photosensitive composition. Thus, it has been known that sensitivity of photosensitive composition is influenced by types of the photopolymerization initiator contained therein.
With the increase of the production volume of a liquid crystal display, the production output of a color filter also has recently increased. Therefore, from the viewpoint of further improvement in productivity, there is a need for a high sensitivity photosensitive composition capable of forming a pattern at a low light exposure.
Under these circumstances, Patent Document 1 proposes, as a photopolymerization initiator capable of improving sensitivity of the photosensitive composition, an oxime ester compound having a cycloalkyl group. Examples described in Patent Document 1 specifically disclose compounds represented by the following chemical formulas (a) and (b).

Patent Document 1: Chinese Unexamined Patent Publication No. 101508744